This invention relates to pressure-actuated circulation valves configured for use in tool strings to be deployed in wells to perform downhole functions.
In completing a product recovery well, such as in the oil and gas industry, several downhole tasks or functions must generally be performed with tools lowered through the well pipe or casing. These tools may include, depending on the required tasks to be performed, perforating guns that ballistically produce holes in the well pipe wall to enable access to a target formation, bridge plug tools that install sealing plugs at a desired depth within the pipe, packer-setting tools that create a temporary seal about the tool and valves that are opened or closed.
Sometimes these tools are electrically operated and are lowered on a wireline, configured as a string of tools. Alternatively, the tools are tubing-conveyed, e.g. lowered into the well bore on the end of multiple joints of tubing or a long metal tube or pipe from a coil, and activated by pressurizing the interior of the tubing. Sometimes the tools are lowered on cables and activated by pressurizing the interior of the well pipe or casing. Other systems have also been employed.
Tubing-conveyed systems have included circulation valves in the tool string to enable pumping fluid from the tubing out into the well bore. Circulation can be useful, for instance, in lubricating and flushing the well bore as the tool is run into the well. Such circulation valves must generally be closed to allow tubing pressure to be increased to activate other tools of the string. Some circulation valves, for instance, have been constructed to close in response to a predetermined hydrostatic well pressure. Some others are closed by dropping a ball down the tubing which plugs a port in the valve.